Predicting the melting temperature and the heat of melting of ionic liquids

The group contribution concept is used and a simple and general method is proposed for estimating phase change properties of ionic liquids. The proposal includes some especial characteristics, such as: (i) the model considers the well-known relation between the melting temperature, the heat of melting, and the entropy of melting; (ii) the model considers that a given group has a contribution value if the group occurs in the cation and another different value if it occurs in the anion; and (iii) the correlation process considers experimental data of melting temperature and heat of melting. Despite its simplicity, the proposed model provides deviations that are similar to other more sophisticated, multiparametric models. The literature analysis and our own results indicate that there are still some unknown facts that determine phase transitions and that models have not been able to include and quantify. All this indicates that the goal of having the most general and accurate model for predicting the melting temperature and melting enthalpy of ionic liquids is still far away. However, the present proposal represents a new attempt for contributing to this interesting puzzle of getting good and reasonable estimates for the melting properties which could help in choosing the appropriate ionic liquid for an existing or new application. © 2021 The Authors